26 U.S.C. § 6664: Definitions and special rules

the amount shown as the tax by the taxpayer on his return, plus amounts not so shown previously assessed (or collected without assessment), over the amount of rebates made. The penalties provided in this part shall apply only in cases where a return of tax is filed (other than a return prepared by the Secretary under the authority of section 6020(b)). No penalty shall be imposed under section 6662 or 6663 with respect to any portion of an underpayment if it is shown that there was a reasonable cause for such portion and that the taxpayer acted in good faith with respect to such portion. Paragraph (1) shall not apply to any portion of an underpayment which is attributable to one or more transactions described in section 6662(b)(6) or to any disallowance of a deduction described in section 6662(b)(10). the claimed value of the property was based on a qualified appraisal made by a qualified appraiser, and in addition to obtaining such appraisal, the taxpayer made a good faith investigation of the value of the contributed property. The term “charitable deduction property” means any property contributed by the taxpayer in a contribution for which a deduction was claimed under section 170. For purposes of paragraph (3), such term shall not include any securities for which (as of the date of the contribution) market quotations are readily available on an established securities market. The term “qualified appraisal” has the meaning given such term by section 170(f)(11)(E)(i). The term “qualified appraiser” has the meaning given such term by section 170(f)(11)(E)(ii). No penalty shall be imposed under section 6662A with respect to any portion of a reportable transaction understatement if it is shown that there was a reasonable cause for such portion and that the taxpayer acted in good faith with respect to such portion. Paragraph (1) shall not apply to any portion of a reportable transaction understatement which is attributable to one or more transactions described in section 6662(b)(6). the relevant facts affecting the tax treatment of the item are adequately disclosed in accordance with the regulations prescribed under section 6011, there is or was substantial authority for such treatment, and the taxpayer reasonably believed that such treatment was more likely than not the proper treatment. is based on the facts and law that exist at the time the return of tax which includes such tax treatment is filed, and relates solely to the taxpayer’s chances of success on the merits of such treatment and does not take into account the possibility that a return will not be audited, such treatment will not be raised on audit, or such treatment will be resolved through settlement if it is raised. the tax advisor is described in clause (ii), or the opinion is described in clause (iii). is a material advisor (within the meaning of section 6111(b)(1)) and participates in the organization, management, promotion, or sale of the transaction or is related (within the meaning of section 267(b) or 707(b)(1)) to any person who so participates, is compensated directly or indirectly by a material advisor with respect to the transaction, has a fee arrangement with respect to the transaction which is contingent on all or part of the intended tax benefits from the transaction being sustained, or as determined under regulations prescribed by the Secretary, has a disqualifying financial interest with respect to the transaction. is based on unreasonable factual or legal assumptions (including assumptions as to future events), unreasonably relies on representations, statements, findings, or agreements of the taxpayer or any other person, does not identify and consider all relevant facts, or fails to meet any other requirement as the Secretary may prescribe. returns filed after the date of the enactment of this Act [ Dec. 18, 2015 ], and returns filed on or before such date if the period specified in section 6501 of the Internal Revenue Code of 1986 for assessment of the taxes with respect to which such return relates has not expired as of such date.”